Sequence determination and anticoagulant and antithrombotic activities of a novel sulfated fucan isolated from the sea cucumber Isostichopus badionotus

► The structure fucan-Ib was determined by ES-MS/MS together with NMR. ► fucan-Ib had high antithrombotic activity but low anticoagulant activity. ► fucan-Ib has a well defined structure and can be readily for quality control. ► The therapeutic potential of fucan-Ib deserves further investigation.